Film for heat sealing and process of heat sealing

ABSTRACT

A film and a laminate using the film as a substrate which both are suitable for heat sealing and a process for heat sealing the film and the laminate are disclosed. The film comprises a blend of (I) at least one member selected from the group consisting of (A) elastomeric block copolymers of vinyl-aromatic compounds with conjugated diene compounds, (B) resinous block copolymers of vinyl-aromatic compounds with conjugated diene compounds and (C) vinyl-aromatic resins and/or modified vinyl-aromatic resins, and (II) an olefinic polymer.

BACKGROUND OF THE INVENTION

This invention relates to a film useful as a heat sealing material, aheat-sealing laminate using the film as a substrate thereof and aprocess for heat sealing the film and the laminate to a plasticcontainer.

Generally, in plastic containers which are widely used for seal packingfoodstuffs such as dairy products and confections, there have chieflybeen used covers made of aluminum foil. When plastic containers aresealed with covers of aluminum foil, the covers are generally bonded tothe containers with a hotmelt type adhesive or solvent type adhesive. Inthe container using such an adhesive when the cover is removed from thecontainer, the adhesive remains on the container. The adhesive thus lefton the container is not desirable hygienically in the least and possiblywill do harm to the human body. On the other hand, a process for heatsealing such plastic containers with a plastic film has also been widelyknown. In this case, the problem ascribable to use of an adhesive is notentailed. But, since the sealing is made between two similar materials,the seal thus formed certainly has ample strength and, for this reason,suffers from the disadvantage that desired peeling of the cover from thecontainer becomes difficult to the extent of opening the container beingmade quite inconvenient. For this process, therefore, the requirementsthat the peeling of the cover from the container should be easy (easyseal peeling) and that the cover provides high heat sealing propertymust be satisfied simultaneously.

To satisfy these contradictory requirements, proper selection of a filmas the sealing material and proper selection of conditions for heatsealing are necessary.

The expression "easy seal peeling" as used in this invention means theproperty of a sealed container whereby in a normal state, the containerremains in a tightly sealed state and, when the cover is peeled from thecontainer, the cover can easily be removed by hand without any breakageto the cover or the container proper, and the expression "normal state"means the state in which the sealed container is transported orotherwise handled in the distribution channel.

SUMMARY OF THE INVENTION

An object of this invention is to provide a film suitable forapplication to plastic containers by heat sealing.

Another object of this invention is to provide a laminate suitable forapplication to plastic containers by heat sealing.

Still another object of this invention is to provide a process for heatsealing plastic containers in such a manner as to satisfy easy peelingof seal and high heat-sealing property at the same time.

Further, the objects of this invention will become apparent from adescription to be given in detail herein below.

DETAILED DESCRIPTION OF THE INVENTION

To accomplish the object described above according to the presentinvention, there are provided a film comprising a blend of (I) at leastone member selected from the group consisting of (A) elastomeric blockcopolymers of vinyl-aromatic compounds with conjugated diene compounds,(B) resinous block copolymers of vinyl-aromatic compounds withconjugated diene compounds and (C) vinyl-aromatic resins and/or modifiedvinyl-aromatic resins, and (II) an olefinic polymer; a laminate usingthe film as a substrate thereof; and a process for applying the film andthe laminate to plastic containers by heat sealing.

In the present invention, the objects of the invention can beaccomplished by using the olefinic polymer and the other component inrespective amounts which give a proper composition ratio. No matter whatcomposition ratio may be used, the proportion of the olefinic polymer inthe whole composition is desired to fall in the range of from 2.5 to 50%by weight. Where the composition is composed of three or morecomponents, the elastomeric block copolymer is desired to account fornot more than 50% by weight, the resinous block copolymer for not morethan 70% by weight and the vinyl-aromatic resin and/or modifiedvinyl-aromatic resin for not more than 90% by weight, respectively, forall the components coexisting with the olefinic polymer in thecomposition.

The composition ratio of the components used in the composition shouldbe selected to suit the particular purpose for which the composition isintended.

In the present invention, styrene or α-methyl styrene is used as thevinyl-aromatic compound and butadiene, isoprene or piperylene is used asthe conjugated diene compound. As the vinyl-aromatic resin, there isused polystyrene. Examples of modified vinyl-aromatic resins which areused in the present invention include styrene-butadiene graftcopolymers, styrene-methyl methacrylate-butadiene copolymers,styrene-acrylonitrile copolymers, and styrene-acrylonitrile-butadienecopolymers.

As the olefinic polymer, there is used at least one member selected fromthe group consisting of ethylene-α-olefin random copolymers,ethylene-vinyl acetate copolymers, ethylene-alkyl acrylate copolymers,propylene polymers, and ethylene-propylene elastomers containing a smallamount of unsaturated compounds having a double bond. Particularlydesirable olefinic polymers for this invention are ethylene-α-olefinrandom copolymers, ethylene-alkyl acrylate copolymers and ethylene-vinylacetate copolymers.

Examples of α-olefins to copolymerize with ethylene to formethylene-α-olefin random copolymers are propylene, butene, pentene andhexene. Of the various copolymers using such α-olefins, the copolymerswith butene-(1) is preferable for the purpose of this invention.Examples of the alkyl radicals in the ethylene-alkyl acrylate copolymersused in this invention include ethyl, propyl, iso-propyl and butyl. Ofthese alkyl radicals, ethyl radical is particularly desirable. The alkylacrylate content of this copolymer is desired to fall in the range offrom 5 to 35% by weight. For the ethylene-vinyl acetate copolymer to beused advantageously for this invention, the vinyl acetate contentthereof is required to fall in the range of from 5 to 35% by weight. Ofvarious propylene polymers, atactic polypropylene is particularlydesirable. These olefinic polymers are used either alone or in the formof a mixture of two or more members.

For the purpose of this invention, any block copolymer can be usedwithout reference to its construction insofar as it is produced by theordinary solution polymerization process using an alkyl lithium as thecatalyst. Similarly, the modified vinyl-aromatic resin can be of anytype insofar as it is made by the ordinary polymerization process.

In this invention, there are used two types of block copolymers whichare elastomeric block copolymers containing styrene in an amount of from10 to 50% by weight and resinous block copolymers containing styrene inan amount of from 50 to 95% by weight. The former copolymers are used inan amount of not more than 50% by weight and the latter copolymers in anamount of not more than 70 % by weight. When the former copolymers areused in an amount exceeding 50% by weight, the tackiness of the blendincreases, so that film forming becomes difficult. When the lattercopolymers are used in an amount exceeding the upper limit mentionedabove, a film of easy seal pealing can not be obtained. Further in thepresent invention, the vinyl-aromatic resin and/or modifiedvinyl-aromatic resin are used in an amount of not more than 90% byweight. When the amount exceeds 90% by weight, the seal conditions whichgive desirable easy seal peeling are not obtained any longer. The amountof the olefinic copolymer is in the range of from 2.5 to 50% by weight,no matter what composition ratio may be involved. When this amount isless than 2.5% by weight, the conditions which give good seal peelingcannot easily be obtained. When it exceeds 50% by weight, theself-tackiness of the film increases so much that film forming becomesdifficult.

In this invention, the film is obtained by blending the components in amixing device such as Henshel mixer or tumbler mixer and directlyextruding the resulting blend through an extruder, or the film may beproduced by extruding the mix into pellets through an extruder andsubsequently melting and extruding the pellets into a film. The filmforming can be effected by any one of the known methods such as theinflation process, T-die process, casting process and calender process.Normally, the inflation process is used.

In the present invention, the film obtained as described above may beused in its single form as the cover for a plastic container. A stillbetter cover for the plastic container may be obtained by using thisfilm as a substrate and superimposing some other plastic film, metalfoil or paper thereon and thereby producing a laminate. Examples of suchother plastic films which are used for this lamination include orientedpolystyrene film, oriented polyethylene terephthalate film, orientedpolypropylene film, polyamide film, oriented polyamide film, cellophaneand the like. Further, these films may be used in a form having aluminumor other inorganic compound such as silica vacuum deposited on thesurfaces. As the metallic foil, there is generally used aluminum foil.

The laminate is obtained by any one of ordinary methods employed for thepurpose of lamination such as extrusion lamination, dry lamination andwet lamination. Examples of adhesive which are used in the drylamination include solvent type adhesive using vinyl acetate and vinylchloride, adhesive containing celluloses such as nitrocellulose, ethylcellulose and acetyl cellulose, and reactive adhesive usingpolyurethane. Examples of adhesive usable in the wet lamination includeadhesive using proteinaceous substances such as casein and gelatin,adhesive using vinyl chloride-vinyl acetate and vinyl acetate-acrylicacid copolymers, acrylic ester copolymer emulsions and vinyl acetateemulsions. In the extrusion lamination, polyolefinic resins and theircopolymer resins may be used. The laminate of this invention canotherwise be obtained by extrusion coating the aforementioned plasticfilm, paper or metallic foil with the resinous composition which wouldbe used in the making of the film according to the present invention.

The laminate obtained as described above is applied by heat sealing tocontainers made of plastic materials such as polystyrene, polyolefins,polyvinyl chloride, polycarbonate, polyamide, and thermoplasticpolyesters. The heat sealing can be carried out by any one of knownmethods such as bar sealing, impulse sealing and hot- plate sealing. Inaddition, high-frequency sealing, ultrasonic sealing and inductionsealing are also used for this purpose.

The heat sealing temperature is variable with the particular material ofthe containers involved, other heat sealing conditions such as pressureand time and the shape of sealing head. When the heat sealing is carriedout by using the ordinary hot plate type heat sealer, the heat sealingtemperature is in the range of from about 100° to about 200° C. Peelstrength is used as the criterion for the easy seal peeling of thecontainer which has been sealed as described above. Generally, easy sealpeeling is obtained when the peel strength is in the range of from 0.3to 1.5 kg/20 mm. Fairly easy seal peeling may be obtained even at thepeel strength exceeding 1.5 kg/20 mm depending on the laminateincorporating the rigid substrate or the material of the containersubjected to heat sealing.

As to materials suitable for the plastic containers, in the case ofpolystyrene containers there are used styrene polymers, impact-resistantstyrene polymers, styrene-butadiene block copolymers, mixtures thereof,styrene-methyl methacrylate-butadiene copolymers, styrene-acrylonitrilecopolymers, styrene-acrylonitrile-butadiene copolymers and other styrenecopolymers. Plastic containers are obtained by subjecting sheets made ofthe aforementioned materials to heat molding, and by injection moldingor injection-blow molding. Polyolefin containers which are used for thepresent invention include those made of low-density polyethylene,high-density polyethylene, polypropylene and their copolymers. Further,paper containers or metallic containers having their surfaces coatedwith the aforementioned plastic materials can also be used for thepurpose of heat sealing of the present invention.

As described above, the film and the laminate produced in accordancewith the present invention possess excellent properties as covers forplastic containers and produce sealed containers which have easy sealingproperty and high seal peeling property.

EXAMPLE 1

In a Henshel mixer, a varying set of components indicated in Table 1were blended in a varying ratio indicated in Table 1. The blend thusobtained was molded by the inflation method under the conditionsindicated belo to form a film of 100μ in thickness. The film was testedfor heat sealing property, film forming property and film property. Theresults are shown in Table 1.

    ______________________________________                                        (Molding conditions)                                                          ______________________________________                                        Extruder        40 m/m, L/D ratio = 22                                        Dies            Spiral, 100 mm in diameter                                    Blow ratio      3.0                                                           ______________________________________                                    

As to the test for heat sealing property, each of the films obtained inthe varying compositions indicated in Table 1 was heat sealed to apudding container made of an impact-resistant styrene resin. The heatsealing property was rated by the o and x scale, wherein o denotes asealing temperature zone of at least 20° C. in which easy seal peelingis obtained and x denotes a sealing temperature of less than 20° C.respectively. The film forming property was rated by the o and x scale,wherein o denotes a composition capable of forming a film by theinflation process and x denotes a composition incapable of forming afilm.

The heat sealing was carried out by use of a cup sealer under 5 to 10kg/cm² of pressure for 1.6 seconds of sealing time.

                  TABLE 1                                                         ______________________________________                                                                         Film                                         Film composition (% by weight)                                                                         Heat    form-                                        Test          SB                 HI    sealing                                                                             ing                              Run  Olefinic elas-   SB   Poly- poly- pro-  pro-                             No.  polymer  tomer   resin                                                                              styrene                                                                             styrene                                                                             perty perty                            ______________________________________                                             (EVA)                                                                    1*   --       60      --   --    40    x     o                                2     5       30      --   --    65    o     o                                3    20       30      --   --    50    o     o                                4    40       30      --   --    30    o     o                                5    20       --      --   --    80    o     o                                6    20       10      20   --    50    o     o                                7    20       15      20   --    45    o     o                                8    50       50      --   --    --    o     o                                9    20       10      50   --    20    o     o                                10   30       20      30   --    20    o     o                                11   40       20      30   --    10    o     o                                12*  --       20      60   --    20    x     o                                13   30       --      50   --    20    o     o                                14   30       20      50   --    --    o     o                                     (EEA)                                                                    15   10       --      90   --    --    o     o                                16   20       --      80   --    --    o     o                                17   40       --      60   --    --    o     o                                18*  --       60      --   --    40    x     o                                19    5       30      --   --    65    o     o                                20   20       30      --   --    50    o     o                                21   40       30      --   --    30    o     o                                22   20       --      --   --    80    o     o                                23   20       10      --   20    50    o     o                                24   20       15      --   20    45    o     o                                25   50       50      --   --          o     o                                26   20       50      10   --    20    o     o                                27   30       30      20   --    20    o     o                                28   40       30      20   --    10    o     o                                29*  --       60      20   --    20    x     o                                30   30       50      --   --    20    o     o                                31   30       50      20   --    --    o     o                                     (Tafmer)                                                                 32    3       --      97   --    --    o     o                                33   15       --      85   --    --    o     o                                34   30       --      70   --    --    o     o                                35   45       --      55   --    --    o     o                                36   30       --      70   --    --    o     o                                37    3       40      57   --    --    o     o                                38   20       20      60   --    --    o     o                                39   40       30      30   --    --    o     o                                40    5        5      90   --    --    o     o                                41   20       60      20   --    --    o     o                                42   30       20      50   --    --    o     o                                43*  --       60      --   --    40    x     o                                44    5       30      --   --    65    o     o                                45   20       30      --   --    50    o     o                                46   40       30      --   --    30    o     o                                47   20       --      --   --    80    o     o                                48   20       10      --   20    50    o     o                                49   20       15      --   20    45    o     o                                50   50       50      --   --    --    o     o                                51   20       10      50   --    20    o     o                                52   30       20      30   --    20    o     o                                53   40       20      30   --    10    o     o                                54*  --       20      60   --    20    x     o                                55   30       --      50   --    20    o     o                                56   30       20      50   --    --    o     o                                ______________________________________                                         *Comparative example                                                          (Note)                                                                        (1) EVA: Ethylenevinyl acetate copolymer ("Evaflex P1905", made by Mitsui     Polychemical, vinyl acetate content 19% by weight)                            (2) EEA: Ethyleneethyl acrylate copolymer ("EEA CopolymerDPDJ 6169", made     by Nippon Unicar, ethyl acrylate content 18% by weight)                       (3) Tafmer: Ethylenebutene (1) random copolymer ("TafmerA 4085", made by      Mitsui Petrochemical, butene (1) content 21% by weight)                       (4) SB elastomer: Styrenebutadiene block copolymer ("Tufprene", made by       Asahi Chemical, styrene content 40% by weight)                                (5) SB resin: Styrenebutadiene block copolymer ("Denka Clearene", made by     Denki Kagaku, styrene content 80% by weight)                                  (6) Polystyrene: Styrene polymer ("Denka Styrol GP", made by Denki Kagaku     (7) HIpolystyrene: Rubbermodified impactresistant styrene polymer ("Denka     Styrol HIE4", made by Denki Kagaku)                                      

EXAMPLE 2

In a Henshel mixer, a varying set of components indicated in Table 2were blended in a varying ratio indicated in Table 2. The resultingblend was converted into pellets by an extruder. The pellets wereextruded into a film of 100μ in thickness by an extruder operated by theinflation process under the same conditions as in Example 1. This filmwas bonded by heat sealing to polystyrene sheet 1 mm in thickness and toa laminate of a polyethylene film superimposed on a polystyrene sheetunder the same sealing conditions as in Example 1 and then tested forpeel strength along the sealed portion. The results are shown in Table2.

                                      TABLE 2                                     __________________________________________________________________________       Film composition                                                           Test                                                                             (% by wt.)                                                                 Run                                                                              Olefinic                                                                           SB        Poly-                                                                             HI poly-                                                                           Material Peel strength (Kg/20 mm)                  No.                                                                              polymer                                                                            elastomer                                                                          SB resin                                                                           styrene                                                                           styrene                                                                            of sheet 120° C.                                                                    140° C.                                                                    160° C.                                                                    180° C.                                                                    200° C.            __________________________________________________________________________       (EEA)                                                                      1  30   40   10   --  20   HI polystyrene                                                                         --  --  0.7 0.8 1.0                       2  30   40   10   --  20   SB resin --  --  0.8 0.9 1.2                       3  30   10   40   --  20   Polyethyrene                                                                           0.8 --  1.2 1.6 --                        4  35   10   35   --  20     "      0.9 --  1.4 1.8 --                           (EVA)                                                                      5  30   10   40   --  20   HI polystyrene                                                                         --  0.7 1.1 --  1.4                       6  30   10   40   --  20   General purpose                                                                        --  0.5 1.2 --  1.4                                                  polystyrene                                        7  30   10   40   --  20   HI polystyrene                                                                         --  0.7     1.0 1.2                       8  30   10   40   --  20   General purpose                                                                        --  0.5 1.2 1.4 --                                                   polystyrene                                        9  30   10   40   --  20   Styrene-MMA-                                                                           --  --  0.5 0.9 1.1                                                  Butadiene                                                                     copolymer                                          10 30   19   40   --  20   Polyethyrene                                                                           0.9 --  1.5 1.8 --                        11 10   10   60   --  20     "      0.1 --  0.4 0.5 --                        12 20   10   50   --  20     "      0.1 --  0.6 0.5 --                        13 30   10   40   --  20     "      0.9 --  1.2 1.3 --                        14 25   10   45   --  20     "      0.3 --  0.9 1.0 --                        15 35   10   35   --  20     "      0.8 --  1.2 1.3 --                        16 25   10   45   --  20     "      0.1 --  0.8 0.9 --                        17 35   10   35   --  20     "      0.3 --  1.0 1.0 --                        (Tafmer)                                                                      18 3    --   97   --  --   HI polystyrene                                                                         0.7 1.2 1.5 --  --                        19 15   --   85   --  --     "      0.5 0.7 0.9 1.0 --                        20 30   --   70   --  --     "      0.4 0.6 0.8 0.9 --                        21 45   --   55   --  --     "      0.3 0.4 0.6 0.7 --                        22 20   10   --   20  50     "      0.4 1.3 1.5 1.5 --                        23 20   15   --   20  45     "      0.3 0.8 1.2 1.5 --                        24 25   10   45   --  20   Polyethyrene                                                                           1.4 --  1.6 2.0 --                        25 15   10   55   --  20     "      1.2 --  1.5 1.6 --                        26 35   10   35   --  20     "      1.4 --  1.7 Break-                                                                            --                                                                        age                           27 45   10   25   --  20     "      1.9 --  2.2 Break-                                                                            --                                                                        age                           28 20   10   --   20  50     "      --  0.1 --  0.4 0.5                       29 20   15   --   20  45     "      --  0.1 --  0.5 0.6                       __________________________________________________________________________     Note 1: The values of peel strength indicated are those obtained by           peeling the seal of a given sample at an angle of 180° at a speed      of 200 mm/min.                                                                Note 2: The vinyl acetate content was 19% by weight in the blends of Run      Nos. 5, 6, 12 and 13, 8% by weight in those of Run Nos. 10 and 11, 25% by     weight in those of Run Nos. 14 and 15 and 28% by weight in those of Run       Nos. 7, 8, 16 and 17 respectively.                                       

EXAMPLE 3

In a Henshel mixer, 40% by weight of ethylene-butene (1) randomcopolymer ("Tafmer-A-4085", made by Mitsui Chemical), 30% by weight ofstyrene-butadiene block copolymer ("Denka Clearene", made by DenkiKagaku, styrene content 80% by weight), 10% by weight ofstyrene-butadiene block copolymer ("Tafprene", made by Asahi Chemical,styrene content 40% by weight) and 20% by weight of an impact-resistatpolystyrene resin ("Denka Styrol HI-E-4", made by Denki Kagaku) werehomogeneously blended. The resulting blend was extruded by the inflationprocess under the same conditions as in Example 1 to obtain a film (A)of 50μ in thickness. Separately, a film (B) was produced from a blendcomposed of 40% by weight of ethylene-vinyl acetate copolymer ("Evaflex1905," made by Mitsui Polychemical, vinyl acetate content 19% byweight), 30% by weight of styrene-butadiene block copolymer (styrenecontent 80% by weight), 10% by weight of styrene-butadiene blockcopolymer (styrene content 40% by weight) and 20% by weight of animpact-resistant polystyrene resin. Various other films weresuperimposed one each on the substrates of A and B films by drylamination using a urethane adhesive to produce laminates. Theselaminates were joined by heat sealing one each to pudding containers ofan impact-resistant polystyrene resin at 160° C. under the sealingconditions of Example 1. The laminates on the containers were tested forvarious properties. The results are shown in Table 3.

                                      TABLE 3                                     __________________________________________________________________________                                  Adaptability                                                      Seal peeling                                                                         Sealing                                                                            to packing   Fold retaining                                                                        Light                                                                                Barrier             Laminate construction                                                                           property                                                                             property                                                                           machine                                                                              Printability                                                                        property                                                                              property                                                                             property            __________________________________________________________________________    1. OPP (30)/Seal film A (50)                                                                    o      o    o      o     --      --     --                  2. PET (12)/Seal film A (50)                                                                    o      o    o      o     --      --     --                  3. OPP (30)/aluminum (10)/Seal                                                                  o      o    o      o     o       o      o                      film A (50)                                                                4. Paper (40)/aluminum (10)/                                                                    o      o    o      o     o       o      o                      Seal film A (50)                                                           5. Aluminum foil (20)/Seal                                                                      o      o    o      o     o       o      o                      film A (50)                                                                6. PET (12)/paper (50)/Seal                                                                     o      o    o      o     o       o      --                     film A (50)                                                                7. PET (12)/Seal film B (50)                                                                    o      o    o      o     --      --     --                  8. OPP (30)/aluminum (10)/Seal                                                                  o      o    o      o     o       o      o                      film B (50)                                                                9. PET having aluminum vacuum                                                    deposited (12)/Seal film B                                                                   o      o    o      o     --      o      o                      (100)                                                                      __________________________________________________________________________     The numerals in parentheses indicate film thicknesses in μ.                (Note)                                                                        1 OPP: Oriented polypropylene resin                                           2 PET: Oriented polyethylene terephthalate resin                              3 Sealing property: Sealed cups using a given laminate and filled with        water were dropped from a height of 50 cm onto a concrete floor and           examined for water leakage. When more than 50% by the cups passed the         test, the laminate was rated as acceptable (o).                               4 Light barrier property: Total light transmittance (%) (ASTMD-1003-61).      When a given sample gave 0%, it was rated as acceptable (o).                  5 Barrier property: Oxygen transmission rate (ASTMD-1434-66: in cc/m.sup.     . 24 hours . atm.) When a given sample gave Occ, it was rated as              acceptable (o).                                                               6 Adaptability to packaging machine: The heating base was examined for        presence or absence of blocking, and the laminate was examined for wrinkl     and warp per heat sealing. When a given sample was found to be free from      these defects, it was rated as acceptable (o).                                7 Printability: Adaptability to the printing machine. When a given sample     was passed through the machine without uneven coloring and zigzagging, it     was rated as acceptable (o).                                                  8 Fold retaining property: When a given sample was bent under a load of 1     kg and, after removal of the load, was kept in a form folded by an angle      of less than 45°, it was rated as acceptable (o).                 

EXAMPLE 4

On the seal film B obtained in Example 3, an aluminum foil of 25 micronsin thickness was superimposed by the extrusion lamination process toobtain a laminate. This laminate exhibited properties which allsatisfied the standards indicated in Example 3.

What is claimed is:
 1. A film for heat sealing which comprises a blendof [I] at least one member selected from the group consisting of (A) anelastomeric block copolymer containing 10 to 50% by weight of styreneand/or alpha-methyl styrene copolymerized with conjugated dienes, (B) aresinous block copolymer containing 50 to 95% by weight of styreneand/or alpha-methyl styrene copolymerized with conjugated dienes, [II] astyrene-butadiene graft-copolymer, and [III] at least one memberselected from the group consisting of ethylene-alpha-olefin randomcopolymers, ethylene-vinyl acetate copolymers, ethylene-alkyl acrylatecopolymers, polypropylene and ethylene-propylene elastomers.
 2. The filmof claim 1, wherein the ethylene-propylene elastomer contains therein asmall amount of unsaturated compounds having a double bond.
 3. The filmof claim 1, wherein the alpha-olefin moiety of the ethylene-alpha-olefinrandom copolymer is selected from the group consisting of propylene,butene, pentene and hexene.
 4. The film of claim 1, wherein the vinylacetate content of the ethylene-vinyl acetate copolymer is in the rangeof from 5 to 35% by weight.
 5. The film of claim 1, wherein thepolypropylene is an atactic polypropylene.
 6. The film of claim 1,wherein the alkyl acrylate content of the ethylene-alkyl acrylatecopolymer is in the range of from 5 to 35% by weight.
 7. The film ofclaim 1, wherein the alkyl radical in the ethylene-alkyl acrylatecopolymer is selected from the group consisting of ethyl, propyl,iso-propyl and butyl.
 8. The film of claim 14, wherein theethylene-alkyl acrylate copolymer is an ethylene-ethyl acrylatecopolymer.
 9. The film of claim 1, wherein the blend is composed of (A)the elastomeric block copolymer of styrene and/or alpha-methyl styrenewith conjugated dienes, (C) [II] and [III].
 10. The film of claim 1,wherein the blend is composed of (B) the resinous block copolymer ofstyrene and/or alpha-methyl styrene with conjugated dienes, [II] and[III].
 11. The film of claim 1, wherein the blend is composed of (A) theelastomeric block copolymer of styrene and/or alpha-methyl styrene withconjugated dienes, (B) the resinous block copolymer of styrene and/oralpha-methyl styrene with conjugated dienes, [II] and [III].
 12. Thefilm of claims 1, 9, 10 or 11, wherein the conjugated diene is selectedfrom the group consisting of butadiene, isoprene and piperylene.
 13. Thefilm of claims 1, 9, 10 or 11, wherein at least one member selected fromthe group consisting of ethylene-alpha-olefin random copolymers,ethylene-vinyl acetate copolymers, ethylene-alkyl acrylate copolymers,polypropylene and ethylene-propylene elastomers is present in the rangeof from 2.5 to 50% by weight.
 14. The film of claims 1, 9, 10 or 11,wherein the copolymer of (A) is not more than 50% by weight, thecopolymer of (B) not more than 70% by weight, [II] is not more than 90%by weight and [III] is in the range of from 2.5 to 50% by weight.